Fedify has just laid out a comprehensive implementation plan for this fep:

https://github.com/fedify-dev/fedify/issues/288#issuecomment-3971459585

The core idea is replacing HTTP(S) URIs with server-independent identifiers: ap:// URIs that use a Decentralized Identifier (DID) as the authority component, rather than a domain name. An object identified as ap://did:key:z6Mk…/actor can live on multiple servers simultaneously and survives any single server disappearing.